Add tests for load_data to robustly handle typical csv issues.

[djinnome]

The new interface for calibrate requires csv files, but there are lots of ways that csv files can fail to provide information in the right format. Test the most common failure modes, such as:

• missing data
• incorrectly typed columns
• mislabled columns
• header columns have one fewer column than data
• alignment issues
• Escaping commas
• Na, NaN, None, '',,

All of these issues will make it difficult to convert a dataframe to a correctly typed tensor.

[sabinala]

I'm going to work off of the branch sa-load-data-tests instead of the branch 434-add-tests-... linked to this issue because it looks like something may be off with that branch? It still has a notebook folder with some but not all of the old notebooks from before.

[SamWitty]

Closed, as offloaded by our CSV data loader.